1. Field of the Invention
The present invention relates to a motor driving apparatus and particularly to a motor driving apparatus for controlling a plurality of motors to displace the position of the control object member with less motor driving units including a pair of semiconductor switches than the motors.
2. Description of the Related Art
In general, a vehicle uses a plurality of motors to displace the position of the control objects member such as power seats and power mirrors or the like and the motor driving units of the same number as the motors are used to individually drive these motors. Moreover, a motor driving apparatus is composed of a plurality of motors, a plurality of motor driving units and a control unit. In this case, it is preferable that the motor driving apparatus is as low in price as possible because the motor driving units in the same number as the motors used must be provided. Therefore, a motor driving unit comprising a pair of relays has been used.
Here, FIG. 5 is a circuit diagram illustrating an example of the essential structure of the known motor driving apparatus. This structure utilizes a motor driving unit including a pair of relays.
As illustrated in FIG. 5, the known motor driving apparatus is composed of a first motor 411, a second motor 412, a third motor 413, a fourth motor 414, a first motor driving unit 421, a second motor driving unit 422, a third motor driving unit 423, a fourth motor driving unit 424, and a control unit 43. In this case, the first motor driving unit 421 includes two relays 441, 442, the second motor driving unit 422 includes two relays 451, 452, the third motor driving unit 423 includes two relays 461, 462 and the fourth motor driving unit 424 includes two relays 471, 472.
The first motor driving unit 421 is connected at one end of coils (not designated with the reference numeral) of the relays 441, 442 to a DC power supply and to a control unit 43 at the other end. The movable contacts (not defined with the reference numerals) of the relays 441, 442 are respectively connected to one end and the other end of the first motor 411. One fixed contacts (not defined with the reference numerals) of the relays 441, 442 are connected to the DC power supply, while the other contacts thereof (not defined with the reference numerals) are grounded. The second motor driving unit 422 is connected to the DC power supply at one end of the coils (not defined with the reference numerals) of relays 451, 452 and to the control unit 43 at the other end. The movable contacts (not defined with the reference numerals) of the relays 451, 452 are respectively connected to one end and the other end of the second motor 412 respectively. The one fixed contacts (not defined with the reference numerals) of the relays 451, 452 are connected to the DC power supply, while the other fixed contacts (not defined with the reference numerals) are grounded. The third motor driving unit 423 is connected to the DC power supply at one end of coils (not defined with the reference numerals) of the relays 461, 462, while to the control unit 43 at the other end. The movable contacts (not defined with the reference numerals) of the relays 461, 462 are respectively connected to the one and the other ends of the third motor 413. The one fixed contacts (not defined with the reference numerals) of the relays 461, 462 are connected to the DC power supply, while the other fixed contacts (not defined with the reference numerals) are grounded. The fourth motor driving unit 424 is connected to the DC power supply at one end of the coils (not defined with the reference numerals) of the relays 471, 472, while to the control unit 43 at the other end. The movable contacts (not defined with the reference numerals) of the relays 471, 472 are respectively connected to the one end and the other end of the second motor 414. The one fixed contacts (not defined with the reference numerals) of the relays 471, 472 are connected to the DC power supply, while the other fixed contacts (not defined with the reference numerals) are grounded.
This known motor driving apparatus operates as follows.
First, when the control voltage for the grounded voltage is supplied to the coil of relay 441 of the first motor driving unit 421 from the control unit 43, the coil is energized to switch the movable contact thereof to the condition illustrated in the figure and thereby the power supply voltage is supplied through the contract switched to one end of the first motor 411. Simultaneously, when the control voltage of the power supply voltage is supplied to the coil of relay 442 of the first motor driving unit 421 from the control unit 43, the coil is not energized to keep the movable contact thereof in the condition illustrated in the figure and thereby the ground potential is supplied through the contact held at the other end of the first motor 411. Therefore, a drive current flows to the other end from one end in the first motor 411 and this first motor 411 rotates in one direction. Thereafter, when the polarity of the control voltage supplied to the first motor driving unit 421 from the control unit 43 is inverted, the movable contacts of the relays 441, 442 are set to the inverted condition of the condition illustrated in the figure and the polarity of the voltage supplied to one end and the other end of the first motor 411 is also inverted, a drive current flows to one end from the other end in the first motor 411 and thereby the first motor 411 rotates in the other direction.
Moreover, when the control voltage same as that supplied to the first motor driving unit 421 from the control unit 43 is supplied to the second motor driving unit 422, third motor driving unit 423 and fourth motor driving unit 424 even in the second motor driving unit 422, third motor driving unit 423, fourth motor driving unit 424, the second motor 412, third motor 413 and fourth motor 414 can respectively be rotated as in the case of rotating the first motor 411. When the two motors, for example, the first motor 411 and second motor 412 are rotated simultaneously in the same direction, the movable contacts of the relays 441, 442 of the first motor driving unit 421 and the movable contacts of the corresponding relays 451, 452 of the second motor driving unit 422 are switched in the same manner by supplying the control voltages of the same polarity to the first motor driving unit 421 and second motor driving unit 422 from the control unit 43 and, as a result, the first motor 411 and second motor 412 are rotated simultaneously in the same direction. Moreover, when the other two motors other than the first motor 411 and second motor 412, for example, the third motor 413 and fourth motor 414 are simultaneously rotated in the same direction, the same process as that explained above is executed.
The known motor driving apparatus explained above uses the motor driving units 421 to 424 including two relays of the same number as that of a plurality of motors 411 to 414 in order to respectively drive a plurality of motors 411 to 414. Therefore this apparatus has a merit that the whole motor driving unit can be formed at a low cost in spite of use of a plurality of motor driving units 421 to 424, but, on the other hand, has a disadvantage that since relays require a comparatively large volume, it is difficult to reduce the size of structure of the motor driving apparatus and moreover switching of contacts during operation of relays is rather noisy.
Therefore, it is also considered to use the motor driving units 421 to 424 including a semiconductor switch pair, for example, the field effect transistor pair in place of the motor driving units 421 to 424 including two relays as a plurality of motor driving units 421 to 424. In this case, it is easy to reduce the size of structure of the motor driving apparatus by utilizing the motor driving units 421 to 424 including the semiconductor switch pair, but the field effect transistor pair that may be used for the motor driving units 421 to 424 of a plurality of motors to displace the position of the control object member is more expensive than the relays and thereby the manufacturing cost of the motor driving apparatus inevitably becomes higher depending on the price of the relays.
On the other hand, when the known motor driving apparatus simultaneously drives two motors, for example, the motors 411, 412, if the driving times of the two motors 411, 412 are identical, since the load for displacing two members as the control object that are respectively coupled with the motors 411, 412 does not become identical, the displacement amounts of two members as the control object do not become uniform and therefore it has been impossible to displace the two members as the control object under the condition that these members are balanced.
The present invention has been proposed considering the technical background as explained above and the first object of the present invention is to provide a motor driving apparatus using a motor driving unit including small size semiconductor switch pairs in order to attain a totally low price motor driving unit by reducing the total number of motor driving units.
Moreover, the second object of the present invention is to provide a motor driving apparatus that can adjust the driving times of two motors to provide uniform displacement amount of positions of the members controlled with two motors on the occasion of simultaneously driving two motors to displace the positions of the members as the control object.
In view of attaining the first object explained above, the motor driving apparatus of the present invention comprises a first structure, including a plurality of motors for displaying the position of a control object member during rotation, a plurality of motor driving units having one or more semiconductor switch pairs to selectively connect a plurality of the motors to the power supply and a control unit for ON/OFF controlling the semiconductor switch pairs of a plurality of motor driving units, wherein a plurality of the motors form at least a set of motors that is formed with two motors, one end of the motors forming a set is connected to a common motor driving unit having one semiconductor switch pair and the other end thereof is connected respectively to a motor driving unit having two semiconductor switch pairs, and the control unit drives, when the two motors forming a set are driven simultaneously, two motors on the time division basis by ON/OFF controlling the two semiconductor switch pairs to provide inverse output voltage polarities of two semiconductor switch pairs of the motor driving unit connected to the two motors.
According to the first structure explained above, a set of motors is formed with two motors among a plurality of motors and one end of two motors forming a set is connected to the motor driving unit that is common to a plurality of motors having a semiconductor switch pair, while the other end thereof is connected to the same motor driving unit having two semiconductor switch pairs to drive, on the time division basis, two motors via the two semiconductor switch pairs of the same motor driving unit. Therefore, the total number of motor driving units required can be reduced in comparison with the total number of motors used and thereby the total size of the motor driving unit can be reduced to realize a low price motor driving unit.
Moreover, in view of attaining the first and second objects explained above, the motor driving apparatus of the present invention comprises a second structure, including a plurality of motors for displacing the position of the control object member during rotation, a plurality of motor driving units having one or more semiconductor switch pairs to selectively connect a plurality of the motors to the power supply, a control unit for ON/OFF controlling the semiconductor switch pair and a displacement amount detecting unit for detecting the position displacement amount of the control object member, wherein a plurality of said motors form at least a set of motors that is formed of two motors, one end of the motors forming a set is connected to a common motor driving unit including one semiconductor switch pair and the other end thereof is respectively connected to a motor driving unit respectively having two semiconductor switch pairs and the control unit drives, when the two motors forming a set are driven simultaneously, the two motors on the time division basis by ON/OFF controlling the two semiconductor switch pairs to provide inverted output voltage polarities of the two semiconductor switch pairs of the motor driving unit connected to the two motors and also adjusts each drive time of two motors to provide an equal position displacement amount of the control object members with two motors detected by the displacement mount detecting unit in regard to the drive time of two motors.
According to the second structure explained above, the function that is same as that attained with the first structure can be attained and since each drive time of these two motors forming a set is adjusted to make equal the position displacement amount of the control object member with two motors forming a set, the position displacement amount of the control object member with two motors driven simultaneously is always kept equal and thereby unbalance condition when the position of the control object member is displaced can be eliminated.
The semiconductor switch pair in the first and second structures is suitably a field effect transistor pair connected in series across the power supply.
With the structure explained above, the semiconductor switch pair can be formed with a small-size integrated circuit that easily enables mounting of the motor driving unit.